<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>系统函数</title>
		<script>
			var str=prompt("请输入一个数字：");
			if(isNaN(str)){
				alert("输入错误");
			}else{
				var k=parseInt(str);
				alert(k);//  NAN
				alert(k+10);
			}
			
		</script>
	</head>
	<body>
	</body>
</html>